CVE-2006-3899 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 on Windows XP SP2 allows remote attackers to cause a denial of service (application crash) by calling the stringToBinary function of the CEnroll.CEnroll.2 ActiveX object with a long second argument, which triggers an invalid memory access inside the SysAllocStringLen function.
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability described in CVE-2006-3899 represents a classic buffer overflow condition affecting Microsoft Internet Explorer 6.0 running on Windows XP Service Pack 2 systems. This issue specifically targets the CEnroll.CEnroll.2 ActiveX object which is part of the Windows Certificate Enrollment component. The flaw manifests when the stringToBinary function is invoked with an excessively long second argument parameter, creating a scenario where the application attempts to allocate memory using the SysAllocStringLen function without proper bounds checking.
The technical execution of this vulnerability involves a memory corruption attack that occurs within the ActiveX component's handling of string parameters. When an attacker supplies a malformed argument exceeding acceptable length limits, the SysAllocStringLen function attempts to allocate memory that exceeds the allocated buffer boundaries, resulting in invalid memory access. This memory corruption causes the Internet Explorer application to become unstable and ultimately crash, leading to a denial of service condition that prevents legitimate users from accessing web content through the affected browser.
From an operational perspective, this vulnerability presents significant risks to enterprise environments where Internet Explorer 6.0 remains in use. The remote exploit capability means that attackers can trigger the denial of service condition without requiring local system access, making it particularly dangerous in corporate networks where users may inadvertently visit malicious websites. The vulnerability affects the core browser functionality and can be exploited through various attack vectors including malicious web pages, email attachments, or compromised websites that load the vulnerable ActiveX control.
The impact of this vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1203, specifically the use of malicious websites to deliver exploits. Organizations should consider implementing browser security restrictions including ActiveX control blocking, enhanced internet zone security settings, and mandatory browser updates to address this vulnerability. The recommended mitigation strategy includes immediate deployment of Microsoft security patches, disabling unnecessary ActiveX controls, and implementing network-based protections such as web application firewalls to prevent exploitation attempts.
This vulnerability highlights the broader security challenges associated with legacy browser components and ActiveX controls that lack proper input validation mechanisms. The issue underscores the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that include browser hardening, user education, and network monitoring to detect and prevent exploitation attempts. Organizations should also consider migrating away from unsupported browser versions to reduce exposure to similar vulnerabilities that may remain unpatched in older software versions.